ZYGAENIDAE
Ten species of this family are found in the British Isles, and six have been recorded in Dorset. They are medium-sized, wingspan 20 to 40 mm., either brilliant red and burnished black (Burnets), or burnished green (Foresters), almost iridescent, day-flying moths that become active in bright sunlight, and all are attracted to flower-heads. Individual species tend to form discrete colonies that vary enormously in size, depending on the size of suitable habitat available. Potential defence mechanisms include cyanide released from tissues at all stages of the life cycle, plus their colour bearing superficial resemblance to iridescent beetles. The larvae are slug-shaped and resemble ‘Blue’ butterfly caterpillars. Most Burnet larvae over-winter once and most feed on the cyanogenic bird’s-foot trefoil (Lotus corniculatus) plant. The Foresters and the five-spot Burnets, respectively, are difficult to identify in all their phases, and often, the biggest clue to identity is afforded by the characteristics of the locality where the moth is found.
|
163 Adscita statices (Linnaeus, 1758) FORESTER A local species in the British Isles, the larva initially mining the leaves of common sorrel (Rumex acetosa) and then feeding on the outer surface of the plant’s lower leaves. In Dorset, the moth is local, frequenting unimproved grassland on calcareous and neutral soils. On optimum sites it can be abundant and in such places may be observed visiting flowers such as knapweed (Centaurea spp.) and field scabious (Knautia arvensis).
164 Adscita geryon (Hübner, 1813) CISTUS FORESTER Notable/Nb A very local species with a restricted distribution in the British Isles, the larva initially blotch-mining the leaves of common rock-rose (Helianthemum nummularium) and later feeding on the underside layer of the leaf, leaving the top intact. The males fly actively in sunshine, but females tend to remain at rest on downland plants. In Dorset, the moth is local, being restricted to unimproved grassland on chalk downland where its foodplant abounds. In the best sites it can be common and in such places may be observed visiting flowers such as knapweed (Centaurea spp.) and field scabious (Knautia arvensis), but such sites are few and far between. Conservation measures should include sympathetic grazing of chalk downland to promote herb-rich communities containing common rock-rose, a plant most often associated with short turf and medium sward unimproved grassland habitats.
165 Jordanita globulariae (Hübner, 1793) SCARCE FORESTER Notable/Na
A rare species in the British Isles known only from a handful of colonies in the south of England, the larva initially blotch-mining the leaves of greater knapweed (Centaurea scabiosa) usually from the underside. The male actively flies in sunshine but the female is more lethargic remaining at rest on downland flora. Occasionally, males of the species undertake prolonged flight at night. In Dorset, the moth has been recorded once and from a light trap run by H J Moore at that time the biology teacher at Claysemoor School. The weather on this occasion was dry and warm with a northerly wind blowing in anticyclonic conditions as indicated by the weather map for 19 June 1967. A number of Scarce Forester colonies are situated between twenty and forty kilometers north and north-north-east of Iwerne Minster in adjoining Wiltshire, and, given the weather conditions at the time, the Dorset individual probably originated from one of these communities.
169 Zygaena filipendulae (Linnaeus, 1758) SIX-SPOT BURNET
A species with a wide distribution across the British Isles, the larva feeding on common bird’s-foot trefoil (Lotus corniculatus). In Dorset, the moth can be found in most situations where the plant grows. It is locally abundant on dry unimproved grassland, verges, embankments and undercliffs, where it may often be seen sitting on hardhead (Centaurea nigra) and field scabious (Knautia arvensis) flower-heads. Elsewhere, it is decidedly local and colonies are usually small and discrete. Adults seem to emerge over a protracted period and may be seen on the wing at any time between the end of May and the middle of August.
170 Zygaena trifolii (Esper, 1783) FIVE-SPOT BURNET
Two races of this species occur in the British Isles and each occupies a different biotype. Until recently, confusion has reigned over the status of all five spotted Burnets in Dorset because adults closely resemble one another. The larva of the Narrow-bordered Five-spot Burnet171 is ‘hairy’ relative to the other Burnet caterpillars, and this difference is a useful determining factor. Furthermore, the distribution of the respective host plant species of the Five-spot Burnets tends not to overlap, so the nature of the habitat is usually helpful in telling the two races apart.
ssp. decreta Verity 1926 A local sub-species found in England and Wales, commonest in the south-west and declining in the south-east, the larva feeding on greater bird’s-foot trefoil (Lotus pedunculatus). In Dorset, the moth is decidedly local forming scattered and small colonies on marshy ground and wet flushes on sandy soils, and within unimproved grassland and broad woodland rides on ill-drained clay soil. In such places it may be common wherein it is often seen visiting greater bird’s-foot trefoil plants and flowers.
ssp. palustrella Verity 1926 A local and decreasing sub-species that is confined to the chalk and limestone soils south of the Thames, the larva feeding on common bird’s-foot trefoil (Lotus corniculatus). In Dorset, this, the smallest burnet, colonises unimproved chalk downland harbouring good stocks of the foodplant. On the best sites it is abundant, and easily observed visiting flower-heads of knapweed and scabious. The overall impression is that this sub-species is doing rather well, albeit locally, and may be bucking the national trend. The adult tends to be on the wing up to a fortnight earlier than ssp. decreta.
decreta palustella
171 Zygaena lonicerae (Scheven, 1777) NARROW-BORDERED FIVE-SPOT BURNET ssp. latomarginata Tutt 1899
This sub-species is widespread across central and eastern parts of England and south-east Wales, the larva preferring meadow vetchling (Lathyrus pratensis) and red clover (Trifolium pratense), but also eating other vetches and peas. The moth is local in Dorset, and tends to be associated with meadow vetchling growing along railway and road-side embankments on chalky soil, and within unimproved grassland chiefly on ill-drained clay soil, but also along the coast, however colonies are rarely large. The adult is on the wing at the same time as the Five-spot Burnet ssp. palustrella170. Narrow-bordered Five-spot Burnet and Five-spot Burnet ssp. decreta170 colonies co-exist at Kingcombe, Rooksmoor and Pamphill. An example of ab. citrina, a form where the red colouration is replaced by yellow, see illustration, was found paired with a typical-form male on the Monkey Jump roundabout in Dorchester by Dave Foot on 21 June 2003.
|
